Camera system

ABSTRACT

A camera system of the kind arranged to store a lens position obtained at a specific point in time prior to automatic focusing by an automatic focusing device and, when an operation member is operated, to forcedly shift the lens to the stored lens position independently of the automatic focusing action is characterized in that: 
     when the lens position is stored at the specific point in time, photographing conditions obtained at that point in time are also stored. The camera is set to be in the photographing conditions stored when the lens is shifted to the stored lens position by the operation of the operation member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a camera which stores information onphotographing conditions such as the distance to an object to bephotographed, the mode of exposure, an exposure correction value, etc.,and is arranged to perform, when necessary, a photographing operation onthe basis of the information stored.

2. Description of the Related Art

Heretofore a camera which is arranged to have the function of theabove-stated kind has been provided with a memory for storing thedistance to an object to be photographed in addition to an automaticfocusing device (hereinafter referred to as an AF device), an automaticexposure device (hereinafter referred to as an AE device), etc.. Forexample, the object distance obtained for a photographing scene isstored for later use. After that, photographing can be performed for thesame specific object without missing any photographic opportunity bycalling up the measured distance data stored and by performing only alight measuring action, although distance and light measuring actionsmust be performed each time for photographing at a differentphotographing position.

In the case of the above-stated conventional camera, objects other thanthe specific object must be photographed in a priority mode and at anexposure correction value suited for each of them. Therefore, if themode and the correction value are not suited for the scene for which thephotographing position is stored, it would be difficult to take anoptimized exposure picture without readjustment of the priority mode,the control value thereof, and the exposure correction value, even ifthe distance measuring ring of the photo-taking lens is moved quickly byusing the measured distance data stored. This impairs the advantageousfeature that a photographing operation can be speedily carried out byvirtue of the stored position of the distance measuring ring.

Further, if the camera is not arranged to have any absolute distanceinformation for moving the distance measuring ring of the photo-takinglens, and if a reproducing action is performed for photographing on thebasis of a previously stored specific object position after one phototaking lens is interchanged with another, the action would beincorrectly performed thereby making accurate focusing impossible.

SUMMARY OF THE INVENTION

It is one aspect of the invention described in the present applicationto provide a camera system of the above-stated kind, wherein: an objectposition obtained at a specific point in time is stored; in addition tothe object position, other photographic conditions such as an exposurevalue, a photographing mode, a correction value, etc., obtained at thatpoint in time are also stored; in reproducing the data thus stored,these photographic conditions are read out along with the objectposition; and focusing and exposure control actions are performed on thebasis of the data thus reproduced or read out.

It is another aspect of the invention to provide a camera system whichin accordance with the object of the invention described above, isarranged to cancel previously stored values when the lens isinterchanged with another lens, so that focusing and other controlactions can be prevented from being performed on the basis of thepreviously stored values even after the interchanging of the lens.

The above and other objects and features of the invention will becomeapparent from the following detailed description of embodiments thereoftaken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a camera system which is arrangedaccording to the present invention as an embodiment thereof.

FIG. 2 is a flow chart showing the storing action of a computing andcontrolling part 11 of the camera shown in FIG. 1.

FIG. 3 a flow chart showing the reproducing action of the computing andcontrolling part 11 shown in FIG. 1.

FIG. 4 a circuit diagram showing the arrangement of the block diagram ofFIG. 1.

FIG. 5 is a flow chart showing the main program of operation of theembodiment shown in FIG. 4.

FIGS. 6(a) and 6(b) are flow charts showing the details of the step 3 ofFIG. 3.

FIG. 7 is a main program flow chart showing the operation of anotherembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The details of the present invention are as described below in the formof preferred embodiments thereof with reference to the accompanyingdrawings:

FIG. 1 shows in a block diagram a camera which is arranged according tothe present invention as an embodiment thereof. Referring to FIG. 1,first storing means 3 is arranged to store measured distanceinformation. Second storing means 9 is arranged to store thephotographing conditions of the camera, such as an AE mode, etc.. When astorage instructing means 1, which consists of switches, etc., and isdisposed on the body of the camera, is turned on, the first storingmeans 3 stores distance information obtained from position detectingmeans 4 and the second storing means 9 also stores, at the same time,information on photographic conditions coming from setting means 10. Aphoto-taking lens 5 consists of an image forming optical system, a lensbarrel which is arranged to carry the optical system, etc.. When acurrent is supplied to a motor (not shown) which is mounted on the lensbarrel, the motor drives a distance ring (not shown) to shift a focusinglens which is not shown but is included in the lens barrel. Distancering position detecting means 4 is arranged to detect the position ofthe distance ring corresponding to the object distance through a changetaking place, for example, in the resistance value of a sliding resistorand to supply information on the distance detected to the first storingmeans 3. A distance measuring optical system 7 is arranged to have aphoto-electric converting element such as a CCD illuminated with lightand to convert the result thereof into an electrical signal. A drivingcontrol circuit 6 consists of a driving member which is a motor mountedon the lens barrel, is arranged to move the focusing lens of thephoto-taking lens 5 backward or forward for focus adjustment and acontrol circuit which is provided for the motor. The light of an objectwhich has passed through the photo-taking lens 5 is photo-electricallycoverted by the distance measuring optical system 7. The defocus degreeof the focusing lens is computed by the system 7 and is supplied to thedriving circuit 6 via first selection means 8. The focusing lens isdriven according to this computed defocus degree for focusing.

A reference numeral 8 denotes the first selection means while a numeral13 denotes second selection means. When reproduction instructing means2, which consists of switches, etc., and is mounted on the camera body,is turned on, the first selection means 8 changes the information inputof the driving control circuit 6 from the output of the distancemeasuring optical system 7 over to that of the first storing means 3;and the second selection means 13 changes the information input ofphotographing condition setting means 10 from the output of a settingmember 12 over to that of the second storing means 9.

The photographing condition setting means 10 is arranged to havephotographing conditions such as the AE mode and an exposure correctionvalue of the camera set there. A photographing condition setting member12 is arranged to permit the photographer to set photographingconditions such as the AE mode, the exposure correction value, etc.while watching a display made by a display part which is not shown butis disposed on the camera body and consists of a liquid crystal panel,etc.. An exposure computing and controlling part 11 is arranged tocompute such exposure information as a shutter time value TV and anaperture value AV and to control the shutter and the aperture of thephoto-taking lens accordingly. The computing and controlling part 11includes a microcomputer.

Photo-taking lens detecting means 14 is arranged to detect whether thephoto-taking lens 5 is mounted on the camera body. When the photo-takinglens 5 is detached from the camera body, the detecting means 14 suppliesa reset signal to the first and second storing means 3 and 9 to eraseinformation stored there.

The operation of the camera is as follows. In an ordinary case, that is,when the reproduction instructing means 2 is not operated, the cameraoperates as follows. When a shutter release button which is not shown islightly pushed, distance and light measuring actions begin. The defocusdegree of the lens computed by the distance measuring optical system 7via the photo-taking lens 5 is transmitted via the first selection means8 to the driving control circuit 6. The lens is driven and moved to itsin-focus position accordingly. The photographing conditions of thecamera such as the AE mode, the setting value thereof, an exposurecorrection value, etc., are set at the photographing condition settingmeans 10 via the photographing condition setting member 12 and thesecond selection means 13. An exposure value is computed by thecomputing and controlling part 11 on the basis of the set information.Then, photographing is performed when the shutter release button ispushed further.

Next, when the storage instructing means 1 is operated, information onthe current position of the distance (measuring) ring is obtained fromthe photo-taking lens 5 via the position detecting means 4 and is storedby the first storing means 3. At the same time, the setting values whichrelate to an exposure and are set by the photographing condition settingmeans 10 are stored at the second storing means 9. These actions are notperformed if the lens detecting means produces information indicatingthe absence of the lens.

Following this, when the reproduction instructing means 2 is operatedafter the lens is operated and the setting values are changed, the firstand second selection means 8 and 13 select the new setting values if thevalues are stored at the first and second storing means 3 and 9.Therefore, the lens driving control circuit 6 drives the lens accordingto the lens position data stored. The photographing condition settingmeans 10 takes in each setting value stored at the second storing means9. Then, the data for the AE mode and the exposure correction valuecomes back to the state obtained when the storage instructing means 1 isoperated. The computing and controlling part 11 then computes andcontrols the shutter speed (time) value TV and the aperture value AV onthe basis of the AE mode and the exposure correction value thus set.Then, actual shooting is performed.

Further, when the lens is dismounted, the value data stored at thestoring means 3 and 9 is erased by the lens detecting means 14.

Next, the operation of the computing and controlling part 11 isdescribed with reference to FIGS. 2 and 3 which are flow charts.Referring to FIG. 2, the storing action is performed as follows. Whenthe storage instructing means 1 is operated, the flow of operation ofthe invention comes to a step 1 only when the lens is found to bepresent at a step 0. Step 1: An exposure compensation value is stored.Step 2: The AE mode data is stored. Step 3: A Tv value data is stored.Step 4: An Av value is stored. Step 5: Data for the position of the lensis stored. The storing action comes to an end at the step 5.

Referring to FIG. 3, the control action for reproduction (reading data)is performed as follows. When the reproduction instructing means 2 isoperated, the routine of FIG. 3 is executed. At a step 10: The flow ofoperation proceeds to a step 11 only when data is in storage. At thestep 11: The exposure compensation value is reproduced (read out). At astep 12: One of AE modes including a program mode, a Tv priority mode,an Av priority mode and a manual mode is reproduced.

At steps 13 and 14: If the AE mode selected is the Tv priority mode orthe manual mode, the Tv value in storage is reproduced. At steps 15 to22: If the mode is the Av priority mode, or the manual mode, the Avvalue in storage is reproduced. However, if the Av value in storage isfound to be smaller than the value AVo of the lens at the step 16,reproduction is made with the value AVo at the step 17. At the step 18,the value AVo is displayed in a flickering state by a display element togive a warning. At the step 19: If the Av value in storage is found tobe larger than the value AVmax of the lens, reproduction is made withthe value AVmax at the step 20. Then, at the step 21, the value AVmax isdisplayed with flickering by the display part to give a warning. In casethat the Av value in storage is found to be within a range between theaperture values AVo and AVmax, the stored Av value is reproduced (readout) at the step 22. At a step 23: The lens position information isreproduced and the reproducing action comes to an end.

FIG. 4 is a circuit diagram showing the details of the block diagram ofFIG. 1. Referring to FIG. 4, a reference symbol LN denotes a lens unitmounted on the camera body. A symbol LMTR denotes a motor which isarranged to move the focusing lens in the direction of the optical axisof the lens. A symbol LPRS denotes a motor control circuit which isarranged to drive and control the motor LMTR. The motor LMTR and thecontrol circuit LPRS jointly form a driving control circuit 6 of FIG. 1.An encoder ENC is a pulse plate which is arranged to produce a number ofpulses corresponding to a change occurred in the position of the lens inassociation with the movement of the lens. A counter CON is arranged tocount the pulses produced from the encoder ENC. The counter CON eithercounts up or counts down according to the rotating direction of themotor LMTR. The counted value of the counter CON represents the currentlens position. The counter CON thus forms the position detecting means 4of FIG. 1. Further, the control circuit LPRS has a memory Ml and isarranged to add together a defocus degree produced from a computer COMvia a port Al and the current counted value of the counter CON and totemporarily store the sum thus obtained at the memory M1. After that,the lens is driven until the count value of the counter CON is caused bythe movement of the lens to come to coincide with the value stored atthe memory M1.

A stepper motor DMTR is arranged to control an diaphragm member. Thecontrol circuit LPRS produces a signal for causing the stepper motorDMTR to drive and control the diaphragm member. A mode setting memberMOD is arranged to permit selection of the exposure mode from among theprogram mode, the manual mode, the shutter priority mode, the aperturepriority mode, etc.. A setting value setting member COR is arranged toset the setting value of the exposure compensation value and that of themanual mode or that of the each of the priority modes. The settingmember COR forms to the setting member 12 of FIG. 1 in conjunction withthe above-stated mode setting member MOD. A light receiving element SNSfor distance measurement consists of a pair of sensors arranged toreceive the light of an object's image through the photo-taking lens. Alight measuring circuit SPC has a light measuring sensor. A switchSW_(M) is arranged to be turned on and off by a manual operation andcorresponds to the storing instruction means 1 of FIG. 1. The cameraincludes a display device DIS. A switch SW_(R) is arranged to be turnedon and off by manual operation and corresponds to the reproductioninstructing means 2 of FIG. 1. The switches SW₁ and SW₂ are arranged tobe turned on respectively by the first and second strokes of operationon a shutter release button which is not shown.

The computer COM is provided with ports Al to All. The computer COM hasa memory serving as the storing means 3 and 9 of FIG. 1 and computingand determining functions serving as the computing and controlling part11, the setting means 10 and selection means 13 and 8 of FIG. 1. Theabove-stated setting member COR consists of three setting parts whichare respectively arranged to set the compensation value, the shuttertime value, and the aperture value. The port A5 of the computer COMwhich corresponds to the setting member COR also consists of three portsfor these three setting parts. A switch SW₃ is arranged to turn on whenthe lens unit is mounted on the camera body and serves as the settingmeans 14 of FIG. 1.

FIG. 5 is a flow chart showing the main program of operation of thecomputer COM of FIG. 4. Referring to FIG. 5, the computer COM checks forthe on-state of the switch SW₁ at a step 1. The step 1 is continuouslyexecuted so long as the switch SW₁ remains off.

When the shutter release button is operated to the extent of its firststroke position to turn on the switch SW₁, the flow of the main programproceeds to a step 1'. At the step 1', a check is made for the on-stateof the switch SW_(R). If the switch SW_(R) is found to be off, the flowproceeds to a step 2. At the step 2, an automatic focusing action iscarried out.

For the automatic focusing action, the output of the distance measuringlight receiving element SNS is supplied to the computer COM via the portA6. The defocus degree of the lens for the object to be photographed iscomputed on the basis of the output of this light receiving element inaccordance with a known algorithm. Information on the defocus degreethus obtained is sent to the control circuit LPRS of the lens unit LN.Upon receipt of the information pertaining to the defocus degree, thecontrol circuit LPRS adds that information to the counted value of thecounter CON. The result of this addition is supplied to the memory M1.The result of this addition supplied to the memory Ml indicates the lensposition at which an in-focus state is obtained for the object locatedat a measured distance. The control circuit LPRS causes the motor LMTRto rotate in the direction corresponding to whether the defocus degreeis positive or negative. The motor drives the focusing lens toward thein-focus position of the lens. In association with the focusing action,the counter CON counts the pulses produced from the encoder ENC. Themotor LMTR is brought to a stop when the counted value of the counterCON comes to coincide with the information on the target (in-focus) lensposition stored at the memory Ml. The lens is thus moved to the targetlens position to have the lens focused on the object located at thedistance measured. At the step 2, when the defocus degree signal iscompletely sent to the lens unit LN, the flow proceeds to a step 3.Therefore, the lens driving action mentioned above is carried outthrough the execution of step 3 and the ensuing steps.

At the step 3, information on the mode selected by the mode settingmember MOD and the value set by the setting value setting member COR issupplied via the ports A4 and A5 to the computer COM. Further, ameasured light signal which is produced from the light measuring circuitSPC is supplied via the port A7 to the computer COM. The computer COMcomputes the set value and the measured light signal in the modecorresponding to the mode signal received. An exposure value (shuttertime and aperture value) is thus obtained for the mode.

Steps 4 and 5: A check is made for the on-states of the switches SW_(M)and SW_(R). If these switches are found to be off, the flow comes backto the step 1. After that, the above-stated steps are repeatedlyexecuted to repeat the automatic focusing and exposure value computingactions so long as the switch SW₁ remains on. Further, if the switch SW₂is turned on by a second stroke operation on the shutter release buttonduring the process of repeating the above stated series of steps, aninterruption takes place to perform a release action for photographingat the exposure value obtained at the step 3.

When the switch SW_(M) is turned on, the flow of the program comes fromthe step 4 to a step 6. The step 6 consists of steps which are identicalwith the steps of FIG. 2. A check is made for the state of the switchSW₃ at the step 0 of FIG. 2. If the switch SW₃ is found to be on thusindicating that the lens unit is mounted on the camera body, the flowcomes to the step 1 of FIG. 2 to have the exposure correction valuewhich is set by the value setting member COR stored at the memory. Atthe step 2 of FIG. 2, the mode signal from the mode setting member MODis stored at the memory. At the steps 3 and 4 of FIG. 2, the exposurevalue set at the step 3 of FIG. 5 is stored. In the event that themanual mode is set, the shutter time and aperture values stored at thesteps 3 and 4 are manually set. In the shutter priority mode or theaperture priority mode, these values are automatically set.

At the step 5 of FIG. 2, the counted value of the counter CON of thelens unit LN, i.e. information on the current lens position, is sent tothe computer COM to have information on the current lens positionstored.

Again referring to FIG. 5, after completion of the storing action of thestep 6 (of FIG. 5), the flow comes to a step 5. At the step 5 andensuing steps, the automatic focusing and exposure computing actions arerepeated as mentioned in the foregoing.

Further, the switch SW_(M) is arranged to be turned on by a pushingoperation performed on a push button which is not shown and to be turnedoff when the button is released from the pushing operation. The storingaction is allowed to be carried out only while the button is pushed.

After each data has been stored at the step 6, the push button isreleased from the pushing operation to have the steps 1 to 5 of FIG. 5repeatedly executed. Then, if the mode, etc. are changed by operatingthe mode setting member MOD and the value setting member COR during thestep repeating process, another exposure value corresponding to the newmode is computed at the step 3.

In case that the switch SW_(R) is turned on under the above-statedcondition, the flow of operation is performed in the following manner.With the switch SW_(R) turned on, the flow proceeds from the step 5 to astep 7. The step 7 consists of the steps of the flow of program of FIG.3 which is described in the foregoing. Referring again to FIG. 3, if thelens unit is found to be mounted on the camera body at the step 10, theflow proceeds to steps 11 and 12. At the steps 11 and 12, the exposurecompensation value and the AE mode signal which have been stored at thesteps 1 and 2 of FIG. 2 are read out (or reproduced) respectively. Step13: The mode signal thus read out is checked. If the signal indicatesthe manual or shutter priority mode, the flow comes to the step 14 toread out the shutter time value stored at the step 3 of FIG. 2. If thesignal read out is found at the step 15 to indicate the manual oraperture priority mode, the flow comes to the step 16. At the step 16,if the aperture value stored at the step 4 of FIG. 2 is found to besmaller than the maximum open F number value AVo, the flow comes to thestep 17 to read out the value AVo as the setting value. Further, in thisinstance, the flow comes to the step 18 to flicker the display made atthe display device DIS to give a warning.

If the maximum open F number value AVo is determined to be smaller thanthe stored aperture value, the flow comes to the step 19. At the step19, a check is made to see if the stored aperture value is larger thanthe maximum stopped-down aperture value AVmax (minimum aperture valueobtainable by stopping down the aperture). If so, the flow comes to thestep 20 to read out the value AVmax as a setting value. The flow thencomes to the step 21 to flicker the display elements DIS to give awarning. Meanwhile, if the value AVmax is found at the step 19 to belarger than the stored aperture value, the flow comes to the step 22 toread out the stored aperture.

Through the steps 13 to 22, the stored shutter time value is alone readout in the shutter priority mode. The stored aperture value is read outin the aperture priority mode if it is between the maximum open aperturevalue and the maximum stopped-down aperture value of the lens. If thestored aperture value represents an aperture larger than the maximumopen aperture value, the maximum open aperture is read out. If thestored aperture value represents an aperture smaller than the maximumstopped-down aperture value, the stored aperture value is read out asthe maximum stopped-down aperture value. Further, in the event of themanual mode, the shutter time value and the aperture value are read outin the same manner as described above.

With the aperture value reading controlled in the above stated manner,the embodiment is capable of adequately handling any lens even in caseswhere the lens is interchanged with another lens of different maximumand minimum aperture values after completion of the above-stated storingaction.

Further, at the step 23, the lens position information which is storedat the step 5 of FIG. 2 is read out and supplied to the memory Ml of thelens unit LN. As a result, the lens is moved to the lens positioncorresponding to the information supplied.

After completion of the step 7 of FIG. 5 which is executed in theabove-stated manner, the flow comes to the step 3 via the step 1'. Inother words, the distance measuring action of the step 2 is omitted asthe switch SW_(R) is in an on-state and the lens is moved to the storedlens position supplied to the memory M1.

FIGS. 6(a) and 6(b) are flow charts showing the program of the exposurecomputing action of the step 3 of FIG. 5. In accordance with thisprogram, if the switch SW_(R) is found off at a step 41, the mode andthe setting values set by the setting members MOD and COR are suppliedat steps 42 and 43. At a step 44, the output of the light measuringcircuit SPC is supplied. In the case of the program mode, a shutter timevalue and the aperture value are obtained on the basis of a compensationvalue and a measured light value set at steps 45, 46, 47 and 49. Thevalues thus obtained are supplied, respectively, to TV and AV registers.

If the switch SW_(R) is found to be in an on-state, the steps 42 and 43are not executed and the measured light value is alone supplied at thestep 44. Then, if the mode signal read out at the step 45 is found to beindicative of the program mode, steps 46, 48 and 49 are executed.Therefore, if the mode read out is the program mode, the shutter timeand aperture values are obtained on the basis of the compensation valueand the measured light value read out.

Further, if the selected mode or the mode read out is not the programmode, the program is executed as shown in steps from 50 through 66.

Therefore, at the step 3 of FIG. 5 after the reproducing action of thestep 7 of FIG. 5, an exposure is computed on the basis of the set valuesstored.

FIG. 7 is a flow chart showing the flow of a program of anotherembodiment of this invention. This flow is about the same as in the caseof the flow of FIG. 5 described in the foregoing. The flow of FIG. 7differs from that of FIG. 5 in the following manner: in this case, thereare provided steps 0' and 0". When the lens unit is dismounted, the flowcomes to the step 0" to reset the stored values stored at the step 6.Once the lens is dismounted, the values before that point of time arereset. This resetting arrangement effectively prevents occurrence of anyproblem that otherwise might arise when a different lens is mounted onthe camera body after stored values are set.

What is claimed is:
 1. A camera system comprising:(a) a focusingmechanism; (b) an exposure control circuit; (c) a storage circuitarranged to store focusing data relative to arbitrary focusing andexposure control data relative to exposure control; and (d) areproducing circuit for driving said focusing mechanism on the basis ofsaid focusing data stored in said storage circuit, said circuit arrangedto shift a focusing state currently set by said focusing mechanism to afocusing state determined on the basis of said focusing data stored atsaid storage circuit and to cause said exposure control data stored atsaid storage circuit to be set at said exposure control circuit in placeof the current exposure control data set at said exposure controlcircuit.
 2. A camera system according to claim 1, wherein said exposurecontrol data relative to exposure control is data for an exposure modeor data for a shutter time value or an aperture value.
 3. A camerasystem according to claim 1, wherein said focusing mechanism is arrangedto perform a focusing action under the control of an automatic focusingcircuit and, when said reproducing circuit is operated, to have thefocusing action controlled on the basis of said stored focusing data bythe operation of said reproducing circuit independently of saidautomatic focusing circuit.
 4. A camera system according to claim 1,further comprising a camera body; a lens unit which is mounted on saidcamera body in a manner interchangeable with other lens units; and areset circuit which is arranged to cancel said stored data when saidlens unit is dismounted from said camera body.
 5. A camera systemaccording to claim 1, further comprising a camera body; a lens unitwhich is mounted on said camera body in a manner interchangeable withother lens units; and an inhibiting circuit which is arranged to rendersaid reproducing circuit inoperative when said lens unit is dismountedfrom said camera body.
 6. A camera system comprising:(a) a photo-takinglens; (b) an automatic focusing circuit which includes a driving circuitfor driving said photo-taking lens and is arranged to automaticallyfocus said lens on an object to be photographed on the basis ofautomatic focusing data; (c) an exposure condition data setting circuitarranged to permit exposure condition data to be set by a manualoperation; (d) an exposure control circuit arranged to perform exposurecontrol on the basis of data set by said data setting circuit; (e) astorage circuit arranged to store focusing data relative to arbitraryfocusing and also to store exposure condition data; and (f) areproducing circuit arranged to transmit to said lens driving circuitsaid focusing data stored by said storage circuit in place of theautomatic focusing data of said automatic focusing circuit, for drivingsaid photo-taking lens on the basis of the stored focusing data, and totransmit to said exposure control circuit said exposure condition datastored by said storage circuit in place of said exposure condition dataset by said exposure condition setting circuit.
 7. A camera systemaccording to claim 6, further comprising a first operation member, saidfirst operation member being arranged to permit data which represents acurrently focused state of said photo-taking lens and said data set bysaid setting circuit to be stored at said storage circuit by theoperation of said member.
 8. A camera system according to claim 7,wherein said exposure condition data is photographing mode data.
 9. Acamera system according to claim 7, wherein said exposure condition datarepresents either a shutter time value or an aperture value.
 10. Acamera system having a camera body and an interchangeable lens unitwhich is detachably mounted on said camera body, comprising:(a) afocusing mechanism for focusing; (b) a storage circuit arranged to storefocusing data relative to arbitrary focusing; (c) a reproducing circuitarranged to shift a focusing state which is currently set by saidfocusing mechanism to a focusing state which is set on the basis of saidfocusing data stored by said storage circuit; and (d) a reset circuitarranged to cancel the data stored at said storage circuit when saidlens unit is dismounted from or newly mounted on said camera body.
 11. Acamera system having a camera body and an interchangeable lens unitwhich is detachably mounted on said camera body, comprising:(a) afocusing mechanism for focusing; (b) a storage circuit arranged to storefocusing data relative to arbitrary focusing; (c) a reproducing circuitarranged to shift a focusing state which is currently set by saidfocusing mechanism to a focusing state which is set on the basis of saidfocusing data stored by said storage circuit; and (d) an inhibitingcircuit arranged to render one or both of said reproducing circuit andsaid storage circuit inoperative while said lens unit is in a state ofbeing dismounted from said camera body.
 12. A camera system having acamera body and an interchangeable lens unit which is detachably mountedon said camera body, comprising:(a) an automatic focusing circuitarranged to form automatic focusing data and to automatically focus aphoto-taking lens on an object to be photographed by causing a lens tobe driven by a lens driving circuit according to said automatic focusingdata; (b) a storage circuit arranged to store data relative to arbitraryfocusing; (c) a reproducing circuit arranged to cause said lens drivingcircuit to drive said lens on the basis of said data stored by thestorage circuit instead of said automatic focusing data; and (d) a resetcircuit arranged to cancel the data stored at said storage circuit whensaid lens unit is dismounted from or newly mounted on said camera body.13. A camera system having a camera body and an interchangeable lensunit which is detachably mounted on said camera body, comprising:(a) anautomatic focusing circuit arranged to form automatic focusing data andto automatically focus a photo-taking lens on an object to bephotographed by causing a lens to be driven by a lens driving circuitaccording to said automatic focusing data; (b) a storage circuitarranged to store data relative to arbitrary focusing; (c) a reproducingcircuit arranged to cause said lens driving circuit to drive said lenson the basis of said data stored by the storage circuit instead of saidautomatic focusing data; and (d) an inhibiting circuit arranged torender one or both of said reproducing circuit and said storage circuitinoperative while said lens unit is in a state of being dismounted fromsaid camera body.
 14. A camera system according to claim 10, furthercomprising a storage control circuit which is arranged to have datastored at said storage circuit by the operation of an operation member.15. A camera system according to claim 11, further comprising a storagecontrol circuit which is arranged to have data stored at said storagecircuit by the operation of an operation member.
 16. A camera systemaccording to claim 13, further comprising a storage control circuitwhich is arranged to have data stored at said storage circuit by theoperation of an operation member.
 17. A camera system according to claim11, wherein said reproducing circuit is arranged to operate in responseto the operation of an operation member.
 18. A camera system accordingto claim 13, wherein said reproducing circuit is arranged to operate inresponse to the operation of an operation member.